20. We should put on our roof for the heating and hot water. A. solar energy B. equipment C. cracks D. solar panels 21. We should use light bulbs in our homes. A. low energy B. little energy C. a bit energy D. efficient 22. In my opinion, nuclear power is not only expensive but also to our environment. A. danger B. dangerous C. rick D. disaster 23. Several governments try to the use of fossil fuels. A. reduce B. increase C. waste D. save 24. It is a good idea to use when travelling long distances. A. cars B. taxis C. private cars D. public transport 25. Wave energy is a source of energy. A. environment friendly B. environmentally friendly C. environmental friendly D. environmentally friendliness 26. Remember to the lights before going to bed. A. turn B. turn off C. turn on D. stop 27. A hydropower station in the North of the country next year. A. was built B. were built C. will be built D. has been built